The present invention relates to an apparatus known as a gripper head for singly picking-up, with the aid of curved needles, the uppermost lying piece of fabric or similar stickable material from a stack of such material pieces, wherein the curved needles are mounted on the ends of hollow cylinders which are arranged concentrically and are rotatable in opposite directions so that the needles contact, penetrate and releasably hold the piece of material.
In the following discussion, for purposes of simplicity and clarity, the present invention will be described with reference to the singling of cloth or fabric pieces. However, it should be understood that the present invention can be used for the singling of other material pieces such as pieces of felt, carpet sections with rough surfaces, knitted pieces, leather pieces, foamed synthetic material pieces and other stacked stickable pieces of material.
Gripper heads have become known from the Austrian Pat. No. 238640. In this device, the surfaces of the cylinders, upon which the needles are mounted, protrude from the casing within which the cylinders are guided. This has the disadvantage that the device is useable only for a single thickness of material that corresponds to the penetration depth of the needles. If thicker or thinner substances are to be taken up singly, a device with longer or shorter needles must be used. A further disadvantage of this device is that the releasing of a piece of material that has been picked-up is relatively complicated. To release the material, the device uses a plurality of compressed air blow-out openings located in the hollow cylinders.
It is an object of the present invention to provide a gripper head of this type that can be used to singly pick-up substances of differing thicknesses and then without the aid of an external energy source, such as compressed air, release them.